We contacted the FBI and Avery's defense team; corresponded with forensic scientists, analytical chemists, and lab technicians; and reviewed more than 700 pages of EDTA-related evidence uploaded by Reddit user Skipp Topp at StevenAveryCase.org.

McCord and his colleagues' eight-page article is a thorough defense to a blood evidence controversy from the 1995 OJ Simpson trial.

The defense team for Simpson, as with Avery's, argued that police had planted evidence using a vial of preserved blood — of which EDTA (short for ethylenediaminetetraacetic acid) is a smoking gun because it's not found naturally in human blood.

A mass spectrometer similar to the ones used to analyze bloodstains for EDTA in the Simpson and Avery cases.Nadina Wiórkiewicz/Wikipedia (CC BY-SA 3.0)Lab tests showed a very small amount of EDTA in some Simpson-case blood evidence. But some experts believe the chemical came from a test sample, not blood from the crime scene.

The test sample was a positive control to show the lab equipment could easily detect tiny concentrations of EDTA. Yet that positive test could have contaminated the high-tech lab gear, carried over a little EDTA into other samples, and potentially compromised key blood evidence.

McCord and his colleagues' 1997 study lays out the steps to follow — and missteps to avoid inadvertent EDTA contamination — if anyone comes around again with claims of planted blood evidence.

In particular, the study explains how to flush out any residual EDTA from tandem mass spectrometry machine (pictured above). It also suggests EDTA is easily detectable in dried stains of preserved blood that are 2 years old.

The FBI told Tech Insider that "the Avery protocol was based off the 1997 study, but was updated based on technology advancements."

An FBI spokesperson refused to detail what "technology advancements" meant, but logic suggests it's practically the same protocol — just with newer, more sensitive, and more capable equipment.

The limits of sensitivity

But what of the FBI's actual 2007 testing process during the Avery case? Was it sensitive enough to detect EDTA?

"If blood is preserved with EDTA there will be a 'boatload' of it present in a bloodstain sample," McCord said. "The question of sensitivity would only arise if the blood was diluted after it was shed."

McCord noted that at the time of the Simpson case, labs could detect about a thousand times less EDTA than there is in a watered-down sample of preserved blood.

"The problem in the OJ case was that this issue (there was no dilution) was lost because of [...] some relatively poor testimony by the experts for both sides," he said.

Today, he says, "modern methods can easily detect" about a million times less EDTA than exists in preserved blood.

A blood stain near the ignition of Halbach's RAV4 that matched Avery's DNA profile. Netflix Practically speaking, this is potentially damning to Avery's defense.

It means that if police did plant Avery's EDTA-preserved blood in Halbach's Toyota RAV4, they would have had to dilute it first to avoid detection by a mass-spec machine.

How much dilution? A lot. Roughly a few drops of preserved blood in a volume of liquid the size of a New York City subway car.

Such highly diluted blood would look more like water than a bloodstain. It probably would not have even been visible in Teresa Halbach's car.

A case still under review

McCord says he's still looking over the 14 EDTA-related evidence exhibits from Avery's trial that we sent him, and it may take him awhile. (Exhibit 446, for example — the FBI lab sheets and reports — is a staggering 638 pages long.)

But a preliminary look at the FBI's measurements of EDTA in blood didn't seem to sway him.

"The analyst who made the measurement is highly competent," he said, noting that they tested the equipment with a positive control (the vial of Avery's preserved blood) and a negative control (swabs of car surfaces near the RAV4 bloodstains, but not on them).

McCord is not the only expert we heard from, and we'll dig into those responses in a future post. We'll also note that McCord worked for the FBI for nine years, from 1989 through 1998, but not in 2007 — when the State of Wisconsin asked the bureau for help with the Avery murder trial. So if anyone is qualified to assess the FBI reports that helped put Avery behind bars, it's one of the guys who helped pioneer the test itself.

Dean Strang, one of Avery's defense lawyers in 2007, declined to comment on the case, deferring instead to fellow defense lawyer Jerry Buting. Buting replied to an initial query, but hasn't responded to our followup queries.

The FBI denied multiple Tech Insider interview requests. When we asked for clarification on what a spokesperson meant by "technology advancements" to the 1997 protocol, we were told to file a Freedom of Information Act request, which we've done.

If you're a forensic scientist, analytical chemist, lab technician, or related expert, and you wish to comment on the following documents — especially exhibit 446, which covers the lab reports, methods, validation, and more — please reach out to: dmosher@techinsider.io